Department of Primatology

Current Project

Foraging Cognition

In order to find highly valued food a primate needs spatial knowledge (where to go?), temporal knowledge (when to go?), ecological knowledge (what are the reproductive strategies of plants, their nutritional contents, past weather conditions and consumption rates of other foragers?) and social knowledge (where do others want to go and what do they know?). My studies attempt to investigate all four components of foraging cognition in humans, apes and monkeys in the same tropical rain forest environment. The results are expected to produce novel insights in to human cognitive evolution.

Chimpanzees

Since 2008 I have been studying the ranging and foraging behaviour of Taï chimpanzees (Pan troglodytes verus), investigating the extent of their botanical knowledge and the cognitive strategies they use to find energy-rich ripe fruit. My studies aim to test for the existence of cognitive capacities that enable mental time travel, such as episodic-like memory and future planning and the contexts in which they are used.

In addition, I investigate how individuals can benefit from the reservoir of botanical knowledge of other community members and their use of social cues to find food. The fission-fusion system of chimpanzees provides a unique opportunity to investigate the costs and benefits of gregariousness in relation to locating food and will increase our understanding of the trade-offs made in human fission-fusion systems.

Observations on five adult chimpanzee females with offspring (<7yrs) were conducted over three consecutive years during the same fruiting seasons and comprise consecutive followings of up to 44 days totalling 275 full days. During these periods we recorded the females’ foraging behaviour, travel routes and food locations from the moment they woke up untill the time they made their sleeping nest. The data are being combined with long-term data (>11yrs.) on feeding and ranging behaviour of our target individuals, the phenology of the fruit trees within their territory and the mapped locations of 15,000 fruit producing tree individuals of the 17 most important species in their core area. My work is conducted in close collaboration with my PhD student Simone Ban from the Université Félix Houphouët Boigny in Côte d’Ivoire.

Mbendjele

Since 2015 I started investigating the extent with which humans use episodic memory and flexible planning in the tropical rainforest environment. I, in addition, plan to investigate their species- and plant-specific knowledge of the temporal distribution of their food and how this knowledge corresponds to that of our closest relatives the chimpanzee that lives in similar forests feeding on the same plant food and humans living in different environments where food can be more easily spotted by sight.

The second part of my studies will focus on the questions whether, when and with whom human rainforest foragers share knowledge about food locations, whether information transfer (by language, vocal or gestural reading) increases food finding efficiency and how information of food locations is valued by the community.

To answer these questions we will record the ranging and foraging behaviour of five Mbendjele Yaka women and their families, living in the rainforest of the northwestern Congo basin bordering the Motaba river, for 28 consecutive days each within two consecutive years during the same fruiting seasons. During these periods we plan to record the women’s foraging behaviour, travel routes and food locations from the moment they leave camp till the moment they end their foraging trip. In addition, to our observational work on the women, we will assess the value of alternative foraging choices (through botanical transects) and will conduct a variety of non-invasive food finding experiments. My team exists of me, my Korean PhD student Haneul Jang, a Congolese PhD student Bill Loubelo and one volunteer (Seung lok Paik) and the study is conducted in close collaboration with Prof. Dr. Christophe Boesch. If you see opportunities for comparative analyses or other use of our data, feel free to contact me.

Mangabey monkeys

In this project I investigate whether sooty mangabeys (Cercocebus atys atys) make use of the sounds of other foragers to increase their food finding or foraging efficiency. We test whether the mangabeys use the sounds of nutcracking chimpanzees (Pan troglodytes verus) and red river hogs (Potamochoerus porcus) to locate and scavenge on the remains of cracked nuts. We, in addition, compare the monkeys’ approach behaviour with that of guinea fowls (Agelastes meleagrides; Guttera pucherani) and rodents (Cricetomys spp., Heliosciurus spp.) that also feed on nuts.

We make use of camera traps placed at a variety of locations in the rainforest of the Taï National Park in Côte d’Ivoire. The work is conducted by my Bachelor student Bryndan van Pinxteren and is co-supervised by Dr. Martijn Egas from the Institute of Biodiversity and Ecosystem Dynamics at the University of Amsterdam. The camera trap data is made available to us by PhD candidate Giulia Sirianni and the Pan African Chimpanzee Project led by Prof. Dr. Christophe Boesch and Prof. Dr. Hjalmar Kühl.